IGI's Light Performance Report is an extra report for round diamonds with top optical performance. It gives a light performance score with sub-scores and an Ideal-Scope image made by ray tracing.
In more detail
It uses only the stone's external proportions, so it doesn't account for heavy inclusions. Our brilliance, fire and scintillation scores are a different measure, from our own models.
On a grading report
A separate IGI report, issued with the grading report.
Related terms
- AGS Ideal Report by GIA: The AGS Ideal Report by GIA is a digital supplement to a GIA report. It gives the American Gem Society's light performance grade, and only AGS Ideal 0 stones get one.
- Ideal cut: "Ideal cut" has three meanings: an IGI comment, a GIA supplement grade, or a sales word. At IGI it marks an Excellent round with narrower proportions; at GIA it appears only as "AGS Ideal".
- Brilliance: Brilliance is the white light that a cut stone returns to the viewer. In our census, it is the share of entering light that leaves through the crown toward the viewer.
- Fire: Fire is the flashes of spectral color that a cut stone sends out. In our census, fire is the share of returned light whose colors leave more than 0.6° apart.
- Cut grade: The cut grade rates how well a diamond's proportions and finish work, from Excellent to Poor. GIA gives it only to standard round brilliants in the D-to-Z color range.